Whole fruit and vegetables have a natural protective coating, called a cuticle, which helps retain moisture and reduce decay. Washing, prior to packaging, removes or weakens the cuticle and the protection it provides causing product quality to degrade and reducing shelf life. As a replacement, the food industry employs edible coatings, primarily waxed or cellulose based, which are applied after washing to offer the same protective benefits as the cuticle. The edible coatings provide numerous benefits, such as maintaining product moisture, reducing bacterial decay, and prolonging shelf life.
Although whole fruits and vegetables remain a staple in the fresh food industry, newly developing markets and customer demand exists for pre-sliced fruits and vegetables which are ready to consume without consumer preparation. While the edible coating protects the exterior of the fruit, once a fruit or vegetable is cut, the exposed interior sections of the fruits and vegetables may be subject to enzymatic browning when some of their cells are severed and exposed during slicing. For example, apples, pineapples, peaches, pears, avocados, strawberries, carrots, and potatoes experience enzymatic browning, adversely affecting their appearance and marketability to a customer.
One method of combating the enzymatic browning includes the blanching process, commonly used in the canned and frozen food industries, which thermally deactivates the enzymes responsible for the enzymatic browning. However, the use of heat in the blanching process adversely affects texture, flavor, and nutritional qualities. As a result the thermal processing is not widely used in the fresh-cut produce industry where preserving natural flavors and textures is often a prime objective.
Alternatively, another form of edible coatings, referred to as anti-browning agents, have become a popular means of controlling enzymatic browning of cut fruit and vegetables. Citric acid, ascorbic acid, and erythorbate acid are examples of commercially available anti-browning agents. Depending on the type of fruit or vegetable to be processed, a solution containing a predetermined amount of anti-browning agents may be used to control enzymatic browning. Additionally, predetermined amounts of calcium, sodium, or other additives may be included in the solution in order to enhance texture. As a result, treating freshly cut slices of fruit and vegetables with a solution containing a small amount of a anti-browning agent, typically about 1-5%, can increase the shelf life of refrigerated packaged fresh-cut produce from a few days to over two weeks.
A commonly used commercial device for coating fruit and vegetable slices includes a trough type vat containing an anti-browning solution. For products that sink to the bottom of the vat, a conveyor belt with protruding paddles, located in the bottom of the vat, transports the slices through the solution. The speed of the conveyor controls the exposure time of the slices to the solution. For products that float, another conveyor with protruding paddles, located over the vat, forces the slices that float into the solution and transports the slices across the vat. Again, the speed of the conveyor controls the exposure time of the slices to the solution.
The fruit and vegetable slices are introduced into the trough at one end, forced through the solution by the conveyors and discharged out the opposite end by conveyor paddles onto a second conveyor where excess solution is drained from the product. Unfortunately, ever though the slices may be fully submerged, uniform exposure of all surfaces is not assured. Often, cut surfaces of fruits and vegetables cling together, forming clumps of slices, which may not dislodge during the coating process. While the conveyor belts and the paddles do contact the slices during the transportation through the vat of solution, the contact fails to provide sufficient agitation to dislodge the slices such that each individual slice moves through the solution independently. As such, surfaces on the inside of clumps of slices may not come into full contact with the solution, resulting in spotty coverage of solution and enzymatic browning on parts of the fruit and vegetable slices.
Furthermore, scrap pieces of fruits and vegetables create organic particles when the product is peeled, cored, and sliced. These organic particles may not be removed during washing and as a result often accumulate in the solution of the vat. Additionally, soluble solids, principally sugars, leach from cut product surfaces and concentrate in the solution. The combination of organic particles and sugars make an excellent growth medium for bacteria. Unfortunately, most anti-microbial compounds are incompatible with the anti-browning agents, making bacteria growth difficult to control without complex and expensive means, such as pasteurization and ultra-filtration. Consequently, expensive sanitary equipment design and strict hygienic operating procedures are required to protect food safety, maintain high product quality levels, and preserve the expensive anti-browning solution. Likewise, coating systems containing large fluid volumes of solution are inherently difficult and costly to maintain.
Therefore, there is a need for a method and apparatus for applying a solution to objects that either both sink or float, with a minimum of charge of treatment solution, with precise control of exposure time to the solution, and with positive product agitation to ensure complete solution exposure to all object surfaces.